This Item is subject to the ATF Ruling 2011-4. This Specifies that you can not own a pistol barrel if you own just the ASR Rifle without having an SBR License. When ordering this part we will need the serial number of your firearm so we can confirm you own a pistol or receive copies of your SBR License. Click Here to get the paperwork needed to get your SBR license.

For a nice breakdown on what this means you can check out this article from thetruthaboutguns.com. It gives a nice overview on how to stay within the law.

For more information about how you can put a stock or folding stock on a pistol check out this article from guntrustlawyer.com. You can also check out the ATF's ruling on stabilizing braces here.